RESUMO
Objective:To outline clinical features in syndrome of resistance to thyroid hormone(RTH) and thyrotropin-secreting pituitary adenoma(TSH adenoma) based on a case series, and to assess the value of octreotide suppression test and high-dose dexamethasone suppression test(HDDST) in differentiating the two diseases.Methods:A total of 22 cases with RTH and TSH adenoma clinically diagnosed in Xiangya Hospital of Central South University from October 2010 to December 2021 were retrieved. The clinical characteristics of the two diseases and results to different tests were analyzed and summarized.Results:(1) The tumors in TSH adenoma patients were larger than those with RTH complicated with pituitary mass, which presented chiasmatic compression on images( P<0.05). (2) In octreotide suppression test, thyrotropin(TSH) inhibition rate in RTH patients was lower than that in TSH adenoma patients( P<0.05). In HDDST, TSH inhibition rate was higher in patients with RTH than in patients with TSH adenoma( P<0.05). (3) The TSH inhibition rate was calculated by receiver operating characteristic(ROC) curve. The sensitivity and specificity of octreotide suppression test were 91.9% and 55.6%, respectively, and the threshold value of TSH inhibition rate was 64.24%. The sensitivity and specificity of HDDST were 54.4% and 89.0%, respectively, and the threshold value of TSH inhibition rate was 65.73%.The combined sensitivity and specificity of the two tests were 77.8% and 90.9%, indicating better diagnostic value( P<0.05). Conclusions:The combination of octreotide suppression test and HDDST is of clinical value in differentiating RTH from TSH adenoma. TSH adenoma is more aggressive than that of pituitary adenoma with RTH.
RESUMO
Syndrome of resistance to thyroid hormone(RTH) is inherited by an autosomal dominant trait, and characterized by elevated thyroid hormone levels with reduced responsiveness of the pituitary and peripheral tissues to thyroid hormone action. All of the reported RTH patients have various mutations in the ligand-binding domain coding region of the thyroid hormone receptor beta gene. A 21-year-old man visited our hospital complaining of fatigue. He had mild thyroid goiter and intermittent palpitation. Thyroid function test showed elevated total T3, free T4, and TSH levels. Levels of TSH free a-subunit and basal pituitary hormones, except prolactin, were normal. MRI of the sellar region showed no abnormal finding. TSH response to TRH stimulation was normal, and TSH values to TRH stimulation after T3 suppression revealed partial response. Sequeuce analysis of the thyroid hormone receptor beta gene confirmed a heterozygous missense mutation in exon 9; and the amino acid alteration was a substitution of a threonine(ACG) for a methionine(ATG) at codon313. Sequeuce analysis of the parents showed no mutation.We report the first case of a man with RTH caused by a de novo mutation(M313T) in TRbeta gene, confirmed by sequeuce analysis.
